clearance vs interval

clearance and interval both are nouns.

Word	Noun	Adjective	Verb	Adverb
clearance	Yes	No	No	No
interval	Yes	No	No	No

As nouns, interval is a hypernym of clearance; that is, interval is a word with a broader meaning than clearance:

clearance: the distance by which one thing clears another; the space between them
interval: the distance between things

Other hypernyms of clearance include separation.

clearance (noun)	interval (noun)
permission to proceed	the distance between things
the distance by which one thing clears another; the space between them	a set containing all points (or all real numbers) between two given endpoints
vertical space available to allow easy passage under something	the difference in pitch between two notes
	a definite length of time marked off by two instants